Synthetic fiber treatment agent composition

A synthetic fiber treatment agent composition comprising

• (A) an amino group-containing polyorganosiloxane, where the terminals of the molecular chain are groups described by general formula
• where each R is selected from a C1 to C20 monovalent hydrocarbon group, a substituted C1 to C20 monovalent hydrocarbon group, and a hydroxyl group, with at least 80 mol % of all the R comprising monovalent hydrocarbon groups and substituted monovalent hydrocarbon groups;
• R2 is a C1 to C10 divalent hydrocarbon group;
• R3 and R4 are each selected from hydrogen atoms, C1 to C20 monovalent hydrocarbon groups, and substituted C1 to C20 monovalent hydrocarbon groups;
• a is an integer from 5 to 5;
• p is an integer from 0 to 2;
• q is an integer from 0 to 3, and r is 0 or 1, where (p+q+r)=3, and at least 30 mol % of all siloxane units per molecule are amino group-containing diorganosiloxane units described by general formula
• where R, R2, R3, R4, and a are the same as above and
• (B) a mixture of a polydiorganosiloxane where y is 0 and an amino group-containing polydiorganosiloxane in which y is an integer of 1 or more, in each case described by general formula
• where each A is selected from a trialkylsilyl group, a hydrogen atom, a C1 to C20 monovalent hydrocarbon group, and a substituted C1 to C20 monovalent hydrocarbon group;
• R, R2, R3, R4, and a are the same as above;
• x is an integer of 1 or more;
• where y/(x+y) is no more than 0.1.